The present invention relates to a fixing apparatus for use in an image forming apparatus such as a copying machine, a printer and a facsimile machine and in particular, to a fixing apparatus for quick start fixing capable of heating instantly.
As a fixing apparatus used for an image forming apparatus such as a copying machine, a printer and a facsimile machine, a heat roller fixing system has widely been used, covering from a low speed machine to a high speed machine and from a monochromatic machine to a full-color machine, as a stable system which is highly completed technically.
However, in the conventional fixing apparatus of a heat roller fixing system, when heating a transfer material or toner, an effect of energy conservation is poor to be disadvantageous on the aspect of energy conservation because it is necessary to heat a fixing roller having large heat capacity, and it is time-consuming to warm a fixing apparatus in the case of printing, resulting in a long printing time (warming-up time), which is a problem.
To solve the problem stated above, there has been proposed a fixing apparatus of a film fixing system wherein a film (a heat fixing film) is used so that a heat roller may have an ultimate thickness of a heat fixing film to be of a low heat capacity, and temperature-controlled heater (a ceramic heater) is directly brought into pressure contact with the heat fixing film to improve thermal conduction efficiency sharply, thereby energy conservation and quick start which hardly requires warming-up time are achieved, and an image forming apparatus employing the fixing apparatus of a film fixing system has been proposed, and both of them are used recently.
Further, as a variation of a heat roller, Japanese TOKKAISHO Nos. 52-106741, 57-82240, 57-102736 and 57-102741 disclose a fixing method wherein a light-transmitting base body is used as a fixing roller (a rotary member for fixing), and heat wave emitted from a halogen lamp (ray irradiating device) provided inside the light-transmitting base body is irradiated on toner for heating and fixing to attain quick start without requiring warming-up time. Further, Japanese TOKKAISHO No. 59-65867 discloses a fixing method wherein a fixing roller (a rotary member for fixing) is structured by providing a light-absorbing layer on the outer circumferential surface of a light-transmitting base body, and light emitted from a halogen lamp provided inside a cylindrical light-transmitting base body is absorbed by the light-absorbing layer provided on the outer circumferential surface of the light-transmitting base body, and toner images are fixed by heat of the light-absorbing layer.
However, in the method disclosed by Japanese TOKKAISHO No. 52-106741 wherein a heat wave emitted from a halogen lamp is irradiated through the light-transmitting base body for heating and fixing toner, and in the method disclosed by Japanese TOKKAISHO No. 59-65867 wherein a fixing roller (a rotary member for heat wave fixing) is structured by providing a light-absorbing layer on the outer circumferential surface of the light-transmitting base body, and a heat wave emitted from a halogen lamp is irradiated on the light-absorbing layer through the light-transmitting base body to fix toner with heat of the light-absorbing layer, there are caused problems of separation or damage of the joint portion with a flange member of an end portion of the light-transmitting base body of the rotary member for heat wave fixing, due to the rotary torque pressure applied on the rotary member for heat wave fixing and to the thermal expansion, because a cylindrical glass member is mainly used as a material of the light-transmitting base body, although energy conservation and quick start with shortened warming-up time are achieved. There are further problems that accuracy of an inside diameter or of an outside diameter of the light-transmitting base body is poor, which makes it difficult for the light-transmitting base body to be centered.
Further, in the disclosure of Japanese TOKKAISHO No. 59-65867, a cylindrical glass member is mainly used as a material of the light-transmitting base body, and a flange member serving as a bearing which is mainly made of metal is used to be fitted in the glass member. In this case, the thermal expansion of the flange member is greater than that of the light-transmitting base body, and when the flange member is made accurately, the light-transmitting base body is cracked from its end portion by the thermal expansion of the flange member, which is a problem. In particular, the glass end portion of the light-transmitting base body is easily broken because it already has microscopic cracks which are caused when the glass end portion is cut, and therefore, the end portion is baked so that it is melted. However, because of the reasons that cracks are not eliminated completely and the end face is deformed to be rounded and swelled, the cracks running from the end portion of the light-transmitting base body which comes in contact with the flange member still tend to be caused easily. Therefore, when the flange member is expanded thermally by heat in the course of fixing, the thermal expansion of the flange member causes cracks which start from the end portion of the light-transmitting base body, which is a problem.